The
cross-Andean split of Western Sirystes S.
albogriseus from Eastern Sirystes S.
sibilator is widely recognised and supported by long-known and striking
differences in vocalizations.Donegan’s (2013) study of vocal variation in the genus
supported this split but also a further three-way split of eastern populations.

Part A would change AOU-SACC treatment to reflect
widespread existing treatments in the ornithological literature and can be
considered independently of the merits of the recent publication cited below.

I know not of two more vocally different but lumped
taxa on the SACC list.This
proposal is long overdue for consideration and its acceptance should be
strongly recommended.

Part B: Split "Eastern Sirystes" into
three species

In Donegan (2013), voice of Sirystes throughout its
range was studied in detail, as well as some specimens and other sources of
records.The abstract includes the
following:

"Vocal
differentiation in the genus was studied using quantitative methods and the
determination of primary, secondary and other kinds of vocalizations for
different populations.The widely
recognized split of Western Sirystes S.
albogriseus of the Chocó (Panama, Colombia and Ecuador) from the more
widespread Eastern Sirystes S. sibilator is
strongly supported by differences in vocal repertoire and quantitative vocal
differentiation.Eastern Sirystes
is itself a superspecies comprised of three allopatric species which are
vocally differentiated (quantitatively and in repertoire) to such an extent
that species rank would be afforded under a modern biological species concept
for: (i) White-rumped Sirystes S. albocinereus of Western Amazonia (in Venezuela, Colombia,
Ecuador, Peru, Bolivia and western Amazonas and Acre states, Brazil); (ii)
Todd's Sirystes S. subcanescens of
North Amazonia (in northern Amazonas, northern Pará and Amapá states in Brazil,
French Guiana and Guyana); and (iii) Sibilant Sirystes S. sibilator (including subspecies atimastus) of the Atlantic and
Cerrado regions (in southern Pará state South through most of the rest of
Brazil to northern Argentina and eastern Paraguay).Considerable variation in the kind of
primary and secondary vocalizations are evident between these four proposed
species, with primary vocalizations of particular taxa appearing as rare or
secondary vocalizations or not being given at all by others.The four proposed species also show
considerable morphological differences in the context of Tyrannidae."

Vocal
differentiation between the Eastern races is further detailed in the paper as
follows.See the discussion,
appendices and large number of sonograms for more information.

·The most
geographically distant pair: Atlantic-Cerrado versus Western Amazonian
populations, differ: (i) in the kind of primary
vocalization, which in the Atlantic-Cerrado are chattering songs and in Western
Amazonia are whistles (App. 4); (ii) diagnosably in the song structure and note
shape of whistles, which in Western Amazonia are always followed by one or more
short notes, a chattering song or downstroke song but
in the Atlantic-Cerrado population, to the extent fragments of downstroke songs can be considered the equivalent of a
whistle, are delivered alone or in sequences of such notes and have a less
symmetrical and more sharply peaked note shape (Figs. 1-2); (iii) to the extent
fragments of downstroke songs can be considered the
equivalent of a whistle, diagnosably and significantly in the maximum acoustic
frequency of whistles (App. 3; Fig. 4A); and (iv) significantly but not
diagnosably in other vocal variables set out in Appendix 3.

·North
Amazonian and Atlantic-Cerrado populations differ: (i)
in the kind of primary vocalization, which North Amazonia are whistles and in
the Atlantic-Cerrado are chattering songs (App. 4); and (ii) in the kind of
secondary vocalization, which in North Amazonia are chattering songs and in the
Atlantic-Cerrado are downstroke songs (App. 4); (iii)
diagnosably and significantly in the length of whistles (App. 3; Fig. 4A); (iv)
provisionally (based on a single recording from North Amazonia), in the note
shape of downstroke songs, with the North Amazonia
recording having an initial upstroke which is slower in reaching the peak; and
(v) significantly but not diagnosably in other variables set out in Appendix 3.

·Western
Amazonian and North Amazonian populations differ: (i)
diagnosably in the song structure of whistles, which are the primary
vocalization for both populations, which in Western Amazonia are always
followed by one or more short notes, a chattering song or downstroke
song but in North Amazonia are delivered alone or in sequences of whistles;
(ii) significantly in maximum acoustic frequency of whistles (App. 3; Fig. 4A),
which narrowly missed the statistical test of diagnosability perhaps due to
sample sizes from North Amazonia, but showed no overlap; (iii) in secondary
vocalization type (which is the chattering song in North Amazonia versus downstroke song in West Amazonia) (App. 4); (iv)
provisionally (based on a single recording from North Amazonia), in the note
shape of downstroke songs, with the North Amazonia
recording having an initial upstroke which is slower in reaching the peak; and
(v) significantly but not diagnosably in other variables set out in Appendix 3.

Distributions
and country lists

Most
textbooks show a widespread range for Sirystes,
but as noted in Donegan (2013) there is almost no evidence for the species
occurring in southern Amazonia or much of western Amazonia, whilst all other
parts of the genus' distribution are corroborated by multiple specimen, sound recording
and trip report based/reserve list records.(See map below).
Populations appear restricted to particular habitats/biogeographical regions
(the Choco, western Amazonia (both sides of the Amazon river), North Amazonia
and Atlantic & Cerrado) rather than to interfluves.The only population limited by a river
is Todd's Sirystes in the southern part of its range, which is limited by the
lower Amazon River (in its widest part).

Vernacular
names

The vernacular names would be those set out in the
Abstract quoted above, which are those of Hellmayr (1927) except that for
"Western Sirystes", which is Ridgely & Greenfield (2001)'s
preference over Ridgway (1907) and Hellmayr (1927)'s "Panama
Sirystes".If
Part B passes, then the "Western/Eastern" nomenclature becomes less
attractive and "Choco Sirystes" could be used instead of
"Western" for albogriseus.Given what happened to the Schiffornis, compass direction-based
names seem better avoided.I will
do a separate proposal on the three 'available' English names for albogriseus in the event that Part B
passes.

Comments from Remsen: “YES to both A and B.Donegan’s published analyses shows that
multiple species should be recognized.”

Comments
from Stiles:
“A definite YES to part A: this split is well documented and widely accepted.
For part B, given their vocal distinctiveness and relatively less extreme
plumage differences as well as the convincing analogy with the closely related Myiarchus, I think that the burden of
proof has shifted towards those who would treat all three as a single species,
so YES.”

Comments
from Pacheco: “Yes (A) due to of
reasons given by Donegan's paper, in accordance with the existing literature
data. A Yes (B) also based on that article and my own experience.”

Comments from Zimmer: “YES to both A and B.The vocal distinctions between the
various populations of Sirystes have long been obvious to those with the
required geographic breadth of field experience, and Donegan has done a good
job of detailing that in his paper.He has also done a good job of highlighting the apparent patchy
distribution of Sirystes as a whole, something that squares with my experience,
but which flies counter to most published range descriptions.These are suboscine birds (unlike the
examples of Thraupis and Turdus mentioned by Manuel), and I see
no reason not to treat their diagnosably different vocalizations as hard-wired,
genetically based characters that are at least on a par with any plumage
characters as being reflective of species-level relationships (or lack
thereof).”

Comments
from Robbins: “YES, to recognizing four Sirystes species.I did
not appreciate that the distribution of the cis-Andean taxa was far more
restricted than what the literature has indicated.Differentiation in plumage and
vocalizations are indeed analogous to Myiarchus
species.”